THERMOFIELD ANALYSIS OF MAGNON SQUEEZING STATE IN THE FERROMAGNET

In this paper, we introduce the self-consistent field approximation to treat with the nonlinear interaction among spin waves. Then temperature-dependent Bogoliubov transformation is introduced to generate a new representation which engenders the transition from the zero temperature to the finite temperature. At last, temperature-dependent quantum fluctuation properties of magnons are discussed in the thermal field. At lower temperature, we find that the fluctuation of spin-component at some given time regions can be below the zero-point fluctuation level of the vacuum state and exhibit a periodical squeezing behavior. In particular, these squeezed effects vanish with the increasing of temperature. These squeezing effects differ from the previous studies.